1. Technical Field
This invention is related to the field of ignition diagnosis systems of automotive internal combustion engines. More particularly, it is related to the field of ignition diagnosis and control systems, and the ability to monitor both the ionization signal and ignition coil charging data during the pre-ignition phase with one ionization signal detection systems.
2. Discussion
The prior art includes a variety of conventional methods for detecting and using ionization current in a combustion chamber of an internal combustion engine. Further, the prior art includes methods and systems for monitoring the process of charging an ignition coil in conjunction with the ionization current detection. In these conventional systems, the ignition system normally outputs an ionization feedback signal to the powertrain control module (“PCM”), which utilizes this ionization feedback signal to diagnose and optimize the performance of the ignition system.
It is desirable for the ionization feedback signal to include not only the in-cylinder ionization signal, for use with the diagnosis and optimization of the in-cylinder combustion, but also ignition coil dwell data related to the charging of the ignition coil. Typically, the ionization feedback signal comprises a time-multiplexed combination of the ionization signal and the ignition coil dwell signal, such that ionization feedback signal comprises the coil dwell signal during the pre-ignition stage and the ionization current during the ignition and post-ignition stage.
This method of time-multiplexing has a number of deficiencies, however. For instance, the ability to identify pre-ignition of combustion in the cylinder is reduced. In order to best identify pre-ignition in a cylinder, it is desirable for the PCM to receive the in-cylinder ionization signal during the pre-ignition stage. Because of the time-multiplexing described above, however, the ionization current is not output to the PCM during the pre-ignition stage and instead receives the ignition coil dwell signal.
In effect, the designer of the conventional ignition system with ionization detection is presented with a design choice of, during the pre-ignition stage, providing either the ionization current signal (and thus losing the ability to monitor and optimize the charging of the ignition coil) or the ignition coil dwell signal (and thus reducing the ability to identify pre-ignition). Other attempts to provide both ignition coil dwell data and pre-ignition data include utilizing a very fast charging ignition coil such that the time when the ionization signal is masked is reduced. It would be desirable to provide an ignition system that allows for the output of both the ionization signal and ignition coil dwell signal during the pre-ignition stage of a cylinder, depending on the operating conditions of the engine, such that ignition coil charging and pre-ignition diagnosis is optimized.